2007 - Chemical & Biomedical Engineering - University of South ...

Dr. John Wiencek
Professor and Dean of Engineering
wiencek@eng.usf.edu
(813) 974-3780
website: http://www.eng.usf.edu/
Education:
Ph.D. Chemical Engineering, Case Western Reserve University 1989
M.S. Chemical Engineering, Case Western Reserve University 1985
B.S. Chemical Engineering University of Cincinnati 1984
Research Interests: Protein Biophysics and Novel Membrane-based Water
Purification. Integral Membrane Protein Crystallization
CHARACTERIZATION OF pH-INDUCED
AGGREGATION AND GELATION OF GLUCAGON
Peptide hormones can form a wide variety of aggregate
states in solution depending on pH and salt
concentrations. For example, insulin and glucagon are
known to both reversibly and irreversibly associate in
solution. In the extreme, solution viscosity increases
dramatically due to irreversible aggregation and
eventually leads to the formation of a gelled phase. Such
behavior can be catastrophic in the medicinal formulations
or during the manufacture of these important drugs.
Batch light scattering (both visible laser light as well as
Xrays) and transmission electron microscopy studies on
aggregating glucagon solutions provide some information
on the initial and final states of this gelation process.
Unlike prior work, this study attempted to provide
geometrical measurements (molecular weights, size,
shape) of the aggregated species during the gelation
process. Some pathways for glucagon aggregation are
suggested from this work. Speciation of the population of
aggregates in time by size exclusion chromatography was
ineffective due to deep bed filtration of large aggregates
with the concomitant increase in back pressure on the
column or re-equilibration of the aggregated species to
monomers (depending on eluent conditions). Our recent
work on Flow Field Fractionation (FFF) suggests that
isolation of highly aggregated peptide is possible via the
combination of FFF and online light scattering methods.
FFF has provided key supporting data for some of our
early results and suggests the gelation process is
catalyzed by pre-existent aggregates that are either in the
glucagon lyophilized powder or formed upon dissolution.
Recent Research Projects:
‣ Physical Characterization of Technospheres
and APIs Assessing Glucagon Gelation
Mechanisms in the Production Environment
‣ Static light scattering studies of OmpFporin:
implications for integral membrane protein
crystallization
Recent Publications:
S, Murugesan, J.M. Wiencek, R. Ren and R.J.
Linhardt, “Benzoate-based room temperature ionic
liquids—thermal properties and glycosaminoglycan
dissolution” Carbohydrate Polymers, 63,
268.(2006).
L. Gakhar and J.M. Wiencek, “A possible additional
role of mineral oil in successful flash cooling,” J of
Applied Crystallography, 38, 945. (2005).
W.F. Jones, M.A. Arnold, and J.M. Wiencek,
“Precipitant-controlled growth of lysozyme crystals in
sodium thiocyanate” Crystal Growth & Design, 4,
1387. (2004).
L.T. Nguyen, J.M. Wiencek, and L.E. Kirsch,
“Characterization methods for the physical stability
of biopharmaceuticals,” PDA Journal of
Pharmaceutical Science and Technology, 57, 429.
(2003).
S.-Y. Hu, J. Li and J.M. Wiencek, “Feasibility of
Surfactant-Free Supported Emulsion Liquid
Membrane Extraction,” J. of Colloid and Interface
Science, 266, 430. (2003).
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